Performance characteristics of cylindrical heat pipes with multiple heat sources

Shabgard, Hamidreza; Faghri, Amir

doi:10.1016/j.applthermaleng.2011.06.026

Cited by 49 publications

(15 citation statements)

References 17 publications

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“…Similar to the thermal network analysis of a conventional TS, the thermal resistances related to vapor flow and axial conduction through the wick (and wall) are usually negligible. However, as discussed in [22], neglecting the axial conduction through the wall/wick can lead to under-prediction of the HP capillary limit (a situation where the capillary pressure induced by the wick is not sufficient to pump the liquid from the condenser to the evaporator section) by as much as about 10%. Also note that, if fins are included on the HP evaporator or condenser sections, they must be accounted for in the determination of R e,ex or R c,ex .…”

Section: Heat Pipe Thermal Resistance (R Hp )mentioning

confidence: 97%

Heat pipe heat exchangers and heat sinks: Opportunities, challenges, applications, analysis, and state of the art

Shabgard

Allen

Sharifi

et al. 2015

International Journal of Heat and Mass Transfer

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226

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Section: Heat Pipe Thermal Resistance (R Hp )mentioning

confidence: 97%

Heat pipe heat exchangers and heat sinks: Opportunities, challenges, applications, analysis, and state of the art

Shabgard

Allen

Sharifi

et al. 2015

International Journal of Heat and Mass Transfer

Self Cite

226

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“…The parametric investigations showed that the assumption of uniform evaporation and condensation in the axial direction is valid only if the wall thermal conductivity is small. Shabgard and Faghri (2011) extended the above model to cylindrical heat pipes with multiple evaporator sections. The two-dimensional heat conduction in the heat pipe's wall was coupled with the liquid flow in the wick and the vapor hydrodynamics.…”

Section: Steady-statementioning

confidence: 99%

Heat Pipes: Review, Opportunities and Challenges

Faghri¹

2014

Frontiers in Heat Pipes

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246

105

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A detailed overview of heat pipes is presented in this paper, including a historical perspective, principles of operations, types of heat pipes, heat pipe performance characteristics, heat pipe limitations, heat pipe frozen startup and shutdown, heat pipe analysis and simulations, and various applications of heat pipes. Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology . The first major contribution was the development and advances of new heat pipes, such as loop heat pipes, micro and miniature heat pipes, and pulsating heat pipes. In addition, there are now many new commercial applications that have helped contribute to the recent interest in heat pipes, especially related to the fields of electronic cooling and energy. For example, several million heat pipes are now manufactured each month since all modern laptops use heat pipes for CPU cooling. Numerical modeling, analysis, and experimental simulation of heat pipes have also significantly progressed due to a much greater understanding of various physical phenomena in heat pipes, as well as advances in computational and experimental methodologies.

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“…The parametric dependence of heat pipe performance on wick properties (thickness, radius of curvature, porosity) and heater diameter was investigated by Pruzan et al [15]; the physical insights from the study were used to design wicks capable of dissipating high heat loads. Other physical mechanisms, such as the effect of viscous drag along the wick substrate on liquid flow in a wick [16] and heat spreading in the wall/wick from localized heat sources [17] can also have a prominent effect on the capillary limit of a heat pipe. Fluid loading in the wick also affects the capillary limit.…”

Section: Introductionmentioning

confidence: 99%

Heat pipe dryout and temperature hysteresis in response to transient heat pulses exceeding the capillary limit

Baraya

Weibel

Garimella

2020

International Journal of Heat and Mass Transfer

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The balance between the capillary pressure provided by the wick in a heat pipe or vapor chamber and the flow resistance to liquid resupply at the evaporator determines the maximum heat load that can be sustained at steady state. This maximum heat load is termed as the capillary limit; operation at steady heat loads above the capillary limit will result in dryout at the evaporator wick. However, different user needs and device workloads can lead to highly transient heat loads in applications ranging from consumer electronic devices to server processors. In these instances, the operation of heat pipes must be assessed in response to brief transient heat loads which could be higher than the notional capillary limit that governs dryout at steady state. In the current study, experiments are performed to characterize the transient thermal response of a heat pipe subjected to heat input pulses of varying duration that exceed the capillary limit. Transient dryout events due to a wick pressure drop exceeding the maximum available capillary pressure can be detected from an analysis of the measured temperature signatures. It is demonstrated that under such transient heating conditions, a heat pipe can sustain heat loads higher than the steady-state capillary limit for brief periods of time without experiencing dryout. If the heating pulse is sufficiently long as to induce transient dryout, the heat pipe may experience an elevated steady-state temperature even after the heat load is reduced back to a level lower than the capillary limit. The steady-state heat load must then be reduced to a level much below the capillary limit to fully recover the original thermal resistance of the heat pipe. This characteristic temperature hysteresis following transient dryout has significant implications for the use of heat pipes for pulsed power dissipation. Further experiments are performed to bound the range of heat loads over which the temperature hysteresis is present following a transient dryout event.

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Performance characteristics of cylindrical heat pipes with multiple heat sources

Cited by 49 publications

References 17 publications

Heat pipe heat exchangers and heat sinks: Opportunities, challenges, applications, analysis, and state of the art

Heat pipe heat exchangers and heat sinks: Opportunities, challenges, applications, analysis, and state of the art

Heat Pipes: Review, Opportunities and Challenges

Heat pipe dryout and temperature hysteresis in response to transient heat pulses exceeding the capillary limit

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